Up to now, my test prints have had two a Dpad and two buttons. I want to reserve these two buttons purely for actions in games such as jump and fire, so I need to think about what else I might need.

The most obvious thing is a power switch. I also want a way to change the volume, and possibly other settings in game. This would be a button that you could press at any time that would break out of the game you were in and change the settings using the Dpad and an action button. Pressing the button (let's call it the option button) again would return you to you game at the point you broke off. Another possibility would be to forget the options screen and just have two buttons for volume up and down.

To this end, my latest test add a power switch and a couple of extra buttons:

I've moved the gaming controls slightly lower down to make space and mounted the switch and buttons on perfboard in the same way as the others. The switch is a simple SPDT affair and the buttons are this type: https://www.coolcomponents.co.uk/en/tactile-switch-buttons-6mm-slim-x-5-pack.html. I went with the two button option in the interests of symmetry and also to make sure that two buttons would fit. I'm not sure that I'll keep it this way and might just have the one button next to the power switch.